1. Field of the Invention
The present invention relates to an automatic balancing device for a rotatable system, in particular, for a hand-held tool such as, e.g., an angular grinder, and including a track which is arranged about the rotational axis of the rotatable system and in which at least one balancing body is displaceably arranged, and an elastic resilient element that presses the at least one balancing body against an inner boundary of the track when the rotational speed of the system is below a predetermined threshold, in order to lock the at least one balancing member against the track inner boundary.
2. Description of the Prior Art
In balancing devices of the type described above, the at least one balancing body is automatically displaced along the track during the operation of the system under the action of forces acting thereon into a position in which it balances the imbalance of the system. When the rotational speed of the system is below a predetermined threshold, the influence of the gravity force of the balancing body is so great that it cannot be held in its balancing position only under the action of centrifugal forces acting thereon. At the low rotational speed and at a standstill, the balancing body is held in its balancing position during operation with aid of locking means. In this way, a lasting good balancing of the rotatable system is insured at all rotational speeds of the rotatable system.
U.S. Pat. No. 3,799,619 discloses a device for damping vibrations and having a track in which a plurality of ball-shaped balancing bodies is arranged. The balancing bodies roll along two rail-shaped O-rings that press the balancing bodies against an inner wall at a standstill. In this way, the balancing bodies become locked at the standstill or at low rotational speeds. At high rotational speeds, the balancing bodies are pressed against the O-rings under the action of centrifugal forces with such a force that the balancing bodies are not pressed any more against the inner wall and can, therefore, move along the track. The balancing bodies roll over a roll-off wall of the housing between the O-rings into a balancing position.
The drawback of the known device consists in that the balancing bodies during operation are supported in the axial direction by the elastic O-rings. As a result, the guidance of the balancing bodies is not sufficiently stable. In addition, in particular at high rotational speeds, the pressure, which the balancing bodies apply to the roll-off wall, is relatively high, which can lead to noticeable wear. At that, the greater part of the abrasive particles is retained between the O-rings and the roll-off wall. This leads to disturbances during rolling of the balancing bodies along the roll-off wall. All in all, the construction of the known device is such that disturbances and inaccuracies often occur, which can result in a not sufficient balancing of the imbalance and in reduction of the service life of the balancing device and the rotatable system. Moreover, the assembly of such devices is associated with relatively large costs.
Accordingly, an object of the present invention is to provide a balancing device in which the foregoing drawbacks are eliminated.
Another object of the present invention is to provide a balancing device having an extended service life.